Ignition and operating arrangement for electric discharge lamps with preheatable incandescent cathodes



April 19, 1960 H. JEDLICKA 2,933,645

IGNITION AND OPERATING ARRANGEMENT FOR ELECTRIC mscmmcs LAMPS wzm PREHEATABLE INCANDESCENT CATHODES Filed NOV. 25, 1955 2 Sheets-Sheet 1 INVENTOR I #A-LMl/T JEDL/CKH BYhd y g ATTORNEYS April 1960 H. JEDLICKA 33,645

IGNITION AND OPERATING ARRANGEMENT FOR ELECTRIC Y DISCHARGE LAMPS WITH PREHEATABLE INCANDESCENT CATHODES v 2 Sheets-Sheet 2 Filed NOV. 25, 1955 g 31 270 30 27a 21 Z 5 i i 28 f 2 31 32 I? a I a I lj 17a 17b 8 29 30b 250 IN VENTOR 1 /54 M07 4501 mm ATTORNEYS limited States Patent IGNITION AND OPERATING ARRANGEMENT FOR ELECTRIC DISCHARGE LAMPS WITH PRE- HEATABLE INCANDESCENT CATHODES Helmut Jedlicka, Schwenningen (Neekar), Germany Application November 25, 1955, Serial No. 549,123

Claims priority, application Germany December 27, 1954 12 Claims. (Cl. 315-100) The invention relates to an ignition and operating arrangement for electric discharge lamps, especially luminescent lamps with preheatable incandescent cathodes.

It is known to ignite such discharge lamps fed from the network with the aid of an ignition switch, the main contacts of which, located in the preheating circuit of the incandescent cathodes, are closed in the initial position and which is provided with the parts, such as a heating element, or a freely stretched hot wire, or a magnetic coil or the like, connected in series in the main circuit leading from the network terminals to the electrodes of the lamp for opening and maintaining in open position the main contacts in the preheating circuit.

According to the invention the parts of the ignition switch connected in series in the main circuit of the discharge lamp are bridged by a switch which is opened by an element causing a delaying effect and this switch is maintained in open position after the lamp has been ignited.

The parts located in the main circuit of the ignition switch may consist of a freely stretched hot wire which opens and maintains in open position the main contacts located in the preheating circuit of the incandescent cathodes through the intermediary of an operating member and at the same time also causes the bridging switch to be kept open by the operating member. The ignition switch may, however, also be an electromagnetic switch and the parts thereof arranged in the 'main circuit may be formed by a magnet coil in the interior of which the contacts of the switch located in the preheating circuit of the incandescent cathodes and also the contacts of the action delaying switch are arranged. A bi-metal strip with current passing through it is preferably used as action delaying member for opening the bridging switch. It is advisable to construct the action delaying member for opening the bridging switch so that it operates so slowly that it opens the bridging switch about 2 seconds after the incandescent cathode current has been switched on.

According to another advantageous embodiment of the invention the arrangement is such that the bi-metal bridging switch makes contact earlier than the main contacts connected in series in the preheating circuit of the incandescent cathodes. Moreover, the bi-metal strip of the bridging switch is also insulated on the movable contact lamina'of the switch located in the preheating circuit. In order to compensate'for any fluctuations in the surrounding temperature it is advisable to construct the bi-metal strip twisted through an angle of 180 and to select its shape so that the portion stretching from the twist point to oneend, preferably the portion extending towards the free end forming the contact point of the bridging switch, is of much smaller cross-section than the other portion of the strip. Consequently the partsof the ignition switch located in the main circuit of the discharge lamp playonlyan unimportant part in determining the preheating time of the incandescent cathode.

A result of the invention is that the problem of opening 2,933,645 Patented Apr. 19, 1960 the ignition and actuating arrangements and maintaining them in open position is simplified so that precise and accurately adjustable ignition standing values with immediate readiness after switching oil are attained. In addition special arrangements hitherto necessary, such as auxiliary series-resistance with negative temperature co-eflicients for increasing the preheating time for the ignition device, special windings for the choke coil and so forth, are superfluous.

Several embodiments of the invention are illustrated by way of example in the ten figures of the accompanying drawings.

Fig; 1 explains the application of the invention in principle;

Figs. 2, 3, 4 and 7 are diagrammatic forms of construction of ignition devices according to the invention which operate with a hot wire with current passing through it in the main circuit leading from network terminals to the lamp electrodes;

Figs. 5 and 6 show an electromagnetic ignition arrange- I ment according to the invention;

Figs; 8 and 9 show the constructional design of an ignition device according to the invention and Fig. 10 shows another embodiment of the invention with hot wire in the main circuit.

The references used in the figures are designated as follows: D is the ignition choke, L is the luminescent lamp provided with two ignition cathodes. S is the switch arranged in the ignition cathode preheating circuit. I

. a The following fundamental description applies to Figs.

1 and 5. The parts connected up in the main circuit (hot wire 5, magnet coil Sp) of the ignition switch are bridged by a switch S through which the preheating current flows and'which has an action delaying member, for example a bi-metal strip, for opening its contacts. ,At the end of the preheating period the contacts of the bridging switch S are opened by the said delaying member, for example the bi-metal strip. The preheating current then passes through the parts of the ignition switch arranged in the main circuit, for example the hot wire 5 or the magnet coil Sp, located in the preheating circuit, which open quickly with the result that the lamp is ignited. The main contacts located in the preheating circuit of the incandescent cathodes are then kept open while the lamp is operating. While the lamp is burning the contacts of the [bridging switch S are also maintained in open position by the operating elements which keep open the main contacts S located in the preheating circuit.

In the form of construction illustrated in Fig. 1 the hot wire 5, through the intermediary of a diagrammatically shown actuating element 6a, 6b, controls both the movable con-tact lamina 8 of the switch S provided in the preheating circuit of the incandescent cathode and also the movable contact lamina 17 of the bridging switch This switch S the resistance of which is smaller than that of the hot wire (e.g. 0.1 as compared with 5 ohms), receives the preheating current from the network over the choke D, spiral of the lamp L, and closed main contacts of the SWitchS It cooperates with an action delaying member, for example a bi-metal strip, so that its contacts only break after some delay, that is at the end of the preheating phase; at the same moment the preheating current flows through the free stretched hot wire 5 which in turn causes the main contacts of the ignition switch S to open or break quickly. The lamp ignites, the operating current, which is weaker than the preheating current,

elements the holding open of the bridging switch S smas es As can be more clearly seen from Fig. 2 the free stretc. ed hot wire 5- controls the switch lever 6 rotatable about 7. A tension spring 13 pulls this switch lever in the direction 16 until the hot wire is stretched. When current flows through the hot wire 5, this becomes heated and longer so that the switch lever 6 is moved in the direction 16 under the action of the spring 13 and in so doing, in abutting against the insulating member 14, moves the spring 8 with the contacts in the direction of the arrow the main contacts 9/1t move apart and the contacts 11/12 also remain broken. The contact 11 is arranged on a bi-rnetal strip 17 which, on being heated, is moved in the direction of the arrow. The terminals 2 and 3 correspond to the main contacts of the switch S in Fig. 1, and the terminals 1 and 4 to those of the heated wire H in Fig. l, which is bridged by the bridging. switch S in this case the bi-metal contact 11/ 12.

The mode of operation is the following:

After switching on, the preheating current flows from one network pole over the terminal 1, bi-rnetal strip 17, contact 11/12, terminal 4, and then over a lamp spiral, terminal 2, main contact 9/1l}, spring 8, terminal 3, a second lamp spiral, and choke to the second network pole. The bi-metal strip deflects after the desired period has elapsed (for example 2 seconds at 220 v., C. surrounding temperature) and lifts the contact 11 slightly off the contact 12 whereupon the current immediately flows through the hot wire 5 causing this to stretch, and, as a result, the above mentioned switch lever movement takes place in the direction of the arrow 16, breaking the main contacts 9/10.

The embodiment according to Fig. 4 operates in a similar manner, only in this instance the contact spring 8 is lacking. The switch lever movement in the direction of the arrow 16 directly separates the main contact 12, mounted on the switch lever, from the second main contact 11.

In the magnetic system shown in Figs. 5 and 6, a small magnet coil Sp is provided instead of the free stretched hot wire, which coil, in the embodiment illustrated in Fig. 6, spreads the iron springs of the terminals 2 and 3 in known manner when under current, that is these springs move in the direction of the small arrow and thus break the main contacts 9 and 10 of the switch S The bridge ing switch S has a bi-metal strip which, in the foregoing examples of construction, after the current has been switched on and the lamp spiral preheated, first briefly breaks, and only thereafter conducts the current through the coil Sp which in turn then breaks the main contacts and retains them in open position in the manner described. At the same time the contacts of the switch S are thereby also kept apart in spite of the fact that the bi-metal strip has itself returned into its initial position.

The construction of the ignition and operating arrangement according to the invention may also be carried out in a different manner, for example, in the magnetic type, by a small iron armature which is controlled by the coil which can also be arranged in the ignition vessel. In particular, the ignition arrangement, as is frequently the case, can be enclosed in a metal or plastic housing, for example a pot, glass vessel or the like and, if necessary, under a vacuum or a suitable gas atmosphere.

It can be considered as a special advantage that the bimetal strip in the arrangement according to the invention, serving as bridging member for a heating spiral, a free stretched hot wire, a magnet coil or the like, must only be made very small and consequently with low heat con-. ductivity, as the contact which it controls is practically without any load at all in view of the small resistance of the hot wire or the like connected in parallel. No sparks at break will occur on the switch S as for example on the main contacts of the switch 8;. Therefore, a very small contact break, that is a very slight lifting of the bi-metal strip is already sufficient to cause an immediate inter-rup 4 tion of the preheating circuit switch S and consequently also the continued keeping open of the bridging switch S Another form of construction of the invention, based on the principle of Fig. 1, is illustrated in Fig. 7. The hot wire 5 here also acts as a rotatable lever 6 which is under the influence of the tension spring 13. The end of the lever 6 acts on an intermediate layer of insulating material 14 which is arranged on the movable contact lamina 8 of the preheating circuit switch S On the end of the contact lamina 8 the movable contact 10 is arranged, this lamina and the stationary contact 9 form the main contacts of the preheating circuit switch S The bi-metal strip 17 is arranged insulated on the contact lamina 8. The free end of the bi-metal strip 17 forms the contact point 11 which, with the stationary contact 12, represents the contact path of the bridging switch S The bridging switch S therefore lies between the terminals 1 and 4.

The bi-metal strip 17 is twisted through an angle of at a point intermediate its length. The free end 17a of the bi-metal strip has a relatively small cross-sectional area as compared with that of the portion 17b serving for securing the strip. The bi-metal strip 17 is of slim tapered form in its longitudinal direction, the widest part of the lamina being at the fixing point of the portion 17b. Such a construction effects a compensation of the influence of fluctuations in the surrounding temperature. The free portion 17a only reacts under current heating in consequence of its smaller cross-sectional area and higher resistance. However, in the event of changes in the surrounding temperature the influence of the portions 17a and 17b is balanced because if, in the event of a change in temperature, for example, the free end 17a were to deflect in the direction to break the contacts 11, 12, the rigid end 17b in front of the middle twist would at the same time bend in the sense to close the contacts 115.

The following should be noted concerning the form of construction illustrated in Fig. 7. if immediate ignition of the luminescent lamp does not take place when the preheating current circuit is broken for the first time, the hot wire 5 cools down and both the bridging switch S andalso the switch S in the preheating current circuit are again closed, so that the original ignition process can commence afresh. Therefore it is important that the bridging switch S makes contact earlier than the switch S in the preheating current circuit so that the hot wire 5 at first remains under current and the incandescent cathodes must be once more preheated before the bridging switch S again breaks. The hot wire 5 is heated and only then is the preheating current circuit switch opened.

If the switch S should make contact earlier than the bridging switch S the incandescent cathode current would at the same time flow through the hot wire Sand cause the switch S to reopen immediately and prevent any reheating of the incandescent cathodes taking place at all.

In Fig. 8 the constructional arrangement of an ignition device according to the invention is illustrated. The switch arrangement of the ignition deviceis fitted inan aluminium pot 21 which has on its bottom a screwthreaded pin 22 for fixing the pot in position. 23 is a cover plate. which might also be formed by sealing com pound'such as et-hoxylineresin. The terminal wires of the ignition device 1, 2,3, 4 lead from thecover plate 23.

The ignition device proper consists of a metal base plate -25 which is fixed on two insulating plates 24 by means of attachment lugs 25a. The insulating plates 24 may be indurated fabric discs and space the inserted part of the ignition device relatively to the, aluminium pot 21. 24a is an inserted bottom plate likewise made of indurated fabric. An insulating plate 27 is also fixed on the base plate 25 by means of rivets 28., The insulating plate 27 has several window-like apertures 27a; The base plate 25 is notrectangular in shape but has recesses which are indicated by dash-lines in Fig. 8. The base plate 25 is electrically connect-ed tothe terminal wire 1 by a connecting lead 250; The base plate 25 has a bent up lug 25b formed by incisions, to which lug the hot wire is fixed. The hot wire 5 may be a chrome-nickel wire of about 0.12 mm. diameter and having a resistance factor of about 5 ohms; it is-fixed on the under side of the base plate 25 by means of the tubular rivet 26a.' The hot wire 5 is secured at its other end to the hub of the operating lever 6. The lever 6 is rotatably mounted on a bearing post 32 which in turn is connected to the insulating plate 27 or insulated from the base plate 25. An angular member 26 is conductively mounted on the metal plate 25 by means of the tubular rivet 26a, which angular member 26 carries the rigid contact 12 of the bridging switch hitherto designated by S A similar metal angular member 30 is fixed on the insulating plate 27 by means of. a rivet 30a, on which member the contact lamina 8 of the switch S incorporated inthe preheating current circuit is mounted by means of a rivet 30b. .The contact lamina 8 carries the movable contact 10 which cooperates with the stationary contact 9 on a metal angular member 31. Both the angular member '30 and also the angular member 31 pass downwards through small windows 27a in the insulating plate28. The feed wire 3 is connected to the angular member 30 by a connecting lead on the underside of the metal plate 25 and the feed wire 2 is connected in a similar manner with the angular member 31. Another angular member 34 is mounted on the insulating plate 28' by means'of a tubular rivet 28; the feed wire ,4 is connected to the extension of this member passing to the underside of the insulating plate 28. The operating lever 6 is acted upon by a tension spring 13; if the hot wire 5 is heated, the lever 6, under the influence of the spring 13 will turn in counterclockwise direction; an insulatingpin, 29 limits the turning'moveme'nt ofthe lever 6. Using intermediate insulating layers 14 the contact lamina of the bi-metal switch is mounted on the co'ntactv lamina 8 and insulated therefrom. This lamina carrying the movable'contact 11 is 'twisted through an angle of 180' intermediate its length; the shape of the bi-metal contact lamina is shown in Fig. 9; this arrangement, as already mentioned, has for its object to compensate out the influence of fluctuations in the surrounding temperature on the bi-metal strip. On being heated by current, only the front narrow tapering portion 17a is subjected to defiexion whereas fluctuations in the surrounding temperature act both on the wide rear portion 17b and also on the front po'rtion 17a which, in view of the twist through 180 bend in opposite directions. The contact lamina 17b is connected to the angular member 34 and to the hub of the lever 6 by a con necting wire 33; the connecting wire 33 passes behind the insulating plate 24 facing the bottom of the pot. Theoperation of the ignition device is such that on heating of the hot wire 5 and the oscillation of the lever 6 the contact-lamina 8 is deflected so that both the pair of contacts 9, 10and also the pair of co'ntacts 11, 12 are broken and maintained in broken position respectively. During this operation the contact point 11, 12 has already been interrupted previously bythe incandescent cathode current 'which flowed through the bi-metal strip 17a, 17b. The contact lamina 17a, 17b is prestressed relatively to the contact lamina 8 in such a manner that, when, on the current ceasing to flow through the hot wire 5, the lever is pulled back into its initial position and releases the contact lamina 8, first the pair of contacts 11, 12 and only thereafter the pair of contacts 9, 10 are closed. A small condenser of about 0.02. f. may be provided on the rear side of the metal base plate 25 electrically situated between the feed termianls 2 and 3. The above described construction of the ignition device on a metal base plate 25 with vertical spacing discs 24 and a plastic insulating plate 27 arranged on the metal base plate in such a manner that the ignition device forms an insertion unit for the aluminium pot, is also of ad- G vantage if the ignition device is constructed withoutsupplementary bi-metal bridging switch S The shown construction of the bi-metal switch 17 which offers immunity from fluctuations in the surrounding temperature in view of its twist located approximately midway its length and of the diflferent electrical resistances of its two halves, is of general practical importance. Consequently such bi-metal strip can beadvantageously used also in other heat controlled arrangements.

Owing to the bi-metal strips 17a and 17b located in a bridging circuit, the following points require consideration for the construction of the bi-metal switch. The switch S should be capable of opening after a delay of about 2 seconds and then, providing it is not held open by the operating member, should be capable of closing quickly. This is attainable by prestressing the bi-metal strip 17a, 17b in its inoperativev position, that is in closed state. A relatively long period of time must then elapse before the bi-metal strip has been heated to such an extent that its prestressed contacts can open. In operative condition the-bi-metal strip is then maintained open by the operatingmember. Only a slight cooling of the bi-metal strip would, however, when it is not held open by the operating member, cause the switch S to close, when further cooling of 'the bi-metal strip to its original temperature would merely result in an increase in the contact pressure. In this manner the switch S requires a relatively long time in order to change over from closed to open position, but only a short time to change over from open to closed position. This latter is of importance when it is not a question of immediate ignition of the lamp.

The construction of the bridging switch S is so chosen that it only interrupts its current path when the current can flow parallel to it through the hot wire 5; on the other hand however, it only closes its current path for example, if the ignition of the lamp has not taken place, when the main contacts of the switch S located in the incandescent cathode circuit are not closed; the switching operations of the bridging switch therefore always take place in a condition relieved from current. Therefore, the contact point 11 can, without hesitation, be formed by the point of the oi-metal strip 17a, without it being necessary to provide an extra small contact plate, because, during the switching operations of the bridging switch S strong contact sparks can never form. Namely, in contact breaking, the induction current impulse of the choke D is balanced by the hot wire 5 and, in contact making, the contacts 9, 10 of the switch S located in the preheating circuit, are not yet closed. I

Whereas the resistance'of the hot wire 5 is about 5 ohms, that of the bi-metal strip is only 0.2 ohm.

To ensure that, during the preheating of the incandescent cathodes, the hot wire is not already heated to such an extent that a breaking of the main contacts 9, 10 of the switch S can occur, it is advisable to preadjust the device so that in cold state there is a small air gap between the operating member 6 and the counter bearing point 14 of the contact lamina'S. Then it cannot happen that the switches.S ...and S2 break contact prematurely under the action of the weakly preheated hot wire 5, that is, before the bi-metal strip 17a, 17b has become heated.

It is not absolutely essential for the bridging switch S to consist of a single pair of contacts 11, 12 and its bi-metal contact lamina to be arranged on the lamina 3 of the switch S located in the preheating circuit. A similarly operating arrangement, in which the said features are not present, is illustrated in Fig. 10. The switch S which first bridges the hot wire 5 is in Fig. 10 formed by two contact laminae, 118 on the one hand and 117a and 117b on the other hand. The contact laminae are arranged on insulating bodies 114. If, when the lamp is switched on, the ignition cathode current first flows, it passes from the terminal 1 over the stationary contact 12, the movable contact 111, contact lamina 118, bi,-

metal laminae 117a, 117b, movable contact. 112 and stationary contact 11 to the. terminal .4. In so doing the hot wire is therefore bridged. The heating of the bi-metal strip 117a, 11712 only breaks the contacts 11, 112 so that current flows through the hot Wire 5. This then breaks the contacts 9, in the manner already described, so that the incandescent cathode current is int'errupted. An insulating pin 120 is arranged on the contact lamina 8, which pin, on the deflection of the contact lamina 8, now also lifts the contact lamina 118 oif the stationary contact 12. Therefore the incandescent cathode circuit remains switched off and the bridging switch. S is held in open position. Thus, even when the bi-metal strip 117a, 117i; has again cooled down and contact is made with the stationary contact 11, the path of the contacts 111, 12 remains open as long as hot wire 5 is being heated; but if the current in the hot wire 5 is interrupted, the contact lamina again returns into its position of rest but allows the contacts 12, 111 to close the circuit before the contacts 9, 10 of the switch S are closed in the pre-heating circuit. Consequently, also in this instance it is ensured in any case that the incandescent cathode current which again commences to flow, is not first conducted over the hot wire 5.

I claim:

1. Ignition and operating arrangement for electric discharge lamps with electrodes and with preheatable incandescent cathodes comprising a preheating circuit for the incandescent cathodes, an ignition switch with contacts which are provided in said preheating circuit and closed in one position, a plurality of terminals, 2. main current circuit leading from the terminals to the lamp electrodes, parts of said ignition switch being con: nected in series in the main circuit, a bridging switch for said parts, a thermo responsive action retarded element cooperating with said bridging switch to open the same and maintain it in open position after ignition of a lamp, said parts located in the main circuit consisting of a free stretched hot wire, and an oscillatable lever actuated by said hot wire to open and maintain in open position the contacts located in the preheating circuits of the incandescent cathodes, and to maintain the bridging switch in open position, said bridging switch having a bi-metal strip through which current flows and which strip has one of the contacts of the bridging switch connected thereto.

2. Ignition and operating arrangement as set forth in claim 1, wherein an insulating intermediate layer is provided with the operating element for the main contacts consists of the oscillatable lever'which is non-conductive and acts over the insulating intermediate layer on the preheating circuit switch consisting of a contact which is one of the contacts of the bridging switch, the other contact of which is carried by the bi-metal strip constituting the action retarding element.

3. Ignition and operating arrangement as set forth in claim 1, wherein the operating element for the main contacts consists of the oscillatable lever which is itself current conducting and carries on its end one of the con- 8 tacts of the bridging switch, the other contact of this switch being arranged on acontact of the action retard ing element, and wherein said oscillatable lever acts on the preheating circuit consisting of a contact lamina through the intermediary of an insulating layer.

4. Ignition and operating arrangement as set forth in claim 1, wherein the operating element in the form of the oscillatable lever is itself current conducting and carries at its end one of the contacts of the bridging switch, the other contact of which is arranged on the action retarding element consisting of the bi-metal strip, said lever also carrying one of the contacts of the preheating circuit. 5. Ignition and operating arrangement as set forth in claim 1,, wherein the preheating circuit switch has an electromagnetic switch comprising a magnet coil, and ferromagnetic contact of the preheating circuit switch are arranged in the axial direction of said magneteoil so that, when the coil is excited, a force is produced which magnetizes the last-mentioned contact and spreads them apart, thus opening the preheating circuit switch.

6. Ignition and operating arrangement as set forth in claim 1, wherein the bi-metal strip extends through the interior of a magnet coil forming part of the preheating ignition switch.

7. Ignition and operating arrangement as set forth in claim 1, wherein the bridging switch comprises the bi-metal strip which is insulated on a movable contact of the preheating circuit switch.

8. Ignition and operating arrangement as set forth in claim 1, wherein the free stretched hot wire constituting part of the ignition switch is guided over an upwardly bent tongue formed on the metal base plate and secured on the underside of the base plate by a tubular rivet serving for fixing a metal angle plate carrying a stationary contact of the bi-metal bridging switch.

9. Ignition and operating, arrangement as set forth in claim 1, wherein a metal angle plate carrying a stationary contact of the bi-metal bridging switch is conductively mounted on the base plate.

10. Bi-metal switch for ignition arrangements, c0m prising a bi-metal strip consisting of two twisted bi-metal sections interconnected by an angularly twisted intermediate section such that the section of the strip extending from the twisted. intermediate section to one end supports a contact member and is of smaller crosssectional area than the other section connected to the twisted intermediate section.

11. Bi-metal switch, as set forth in claim 10, wherein the bi-metal strip is of slim tapered shape.

12. Bi-metal switch as set forth in claim 10, wherein the bi-metal strip is of slim tapered shape and its length from a fixed point to an other end isapproximately 8 to 10 times the width at the fixed point.

References Cited in the file of this patent UNITED STATES PATENTS 2,279,060 Rimbach Apr. 7, 1942 2,438,557 Hehenkamp' Mar. 30, 1948 2,476,330 Sitzer g.---- July 19. .1949 

